I presume you are using the 32 bit version of Fedora. I had suffered for a long time before solving the problem for my system.

I took the Fedora Core Distribution DVD from October 24th and found the RPM on it that has the Xorg program. (The rpm will show that the Xorg is to install into the /usr/bin directory. Copy this rpm Xorg program into the same directory to replace /usr/bin/Xorg.

Apparently, an update that was released around Nov 20th of 2006 caused the problem for me. It probably does the same for you. Check out i810

I have always had some issue with monitor res. on linux redhat 9.0, FC3, FC6. Please before you start troubleshooting any of the display problems make sure you have updated the system, yum works well most of the time.

your issued looks to me more of a resolution mismatch, dig out your monitor manual and check what modes it supports and what are the supported frequencies...